Flexible area launch tube rear cover

ABSTRACT

A rear cover for rocket launch tubes providing a seal between the tube and the rear of the rocket. The rocket is arranged in a manner such that the exhaust of a firing rocket will produce a seal between a sealing member and the rear of the rocket and will seal off the portion of the tube adjacent to the rocket itself, thus preventing exhaust gases from entering this portion of the launch tube.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a system for: (a) the sealingof a rocket launch tube prior to lift-off of the rocket contained in thelaunch tube, thus preventing the flow of exhaust gases into the tubearea around the rocket itself; and (b) preventing the exaust gases fromflowing around the rocket during the flyout of the rocket from thelaunch tube.

2. Description of the Prior Art

For military applications rockets, missiles, or other exhaust-gaspropelled vehicles are often stored in closely adjacent magazines,chambers or launch tubes. In these cases, exhaust gas ducts are normallyprovided to convey rocket exhaust gases generated during rocket ignitionto a safe location. Where available space is at a premium, as forexample on board ship, manifolding of a number of closely adjacentlaunch tubes or chambers into a common exhaust manifold or plenumchamber is often necessary.

Various problems may develop if ducts connecting launch tubes to acommon exhaust manifold are normally open before launch of the vehicles.If one or more of these rockets is intentionally or accidentallyignited, portions of the resulting exhaust gases, which may havetemperatures as high as 6,000° F., can be circulated through the commonmanifold, into the connecting ducts and into other launch chambers. Thiscould ignite other rockets. Also, the warheads in the launch chamberscould be detonated by these hot gases. At a minimum, the gases coulddamage the rocket, associated equipment and hold-down devices. Thusaccidental or intentional ignition of one rocket could render a wholeship or launching system ineffective. In addition, if the some of thelaunch tubes are open at their upper ends, exhaust gases entering thechambers through the connecting ducts could escape through the openouter ends. This event could cause further heat or other damage.

To prevent such an occurrence, various types of safety doors and valveshave been proposed in the past. These are normally installed either atthe exhaust gas outlet of each launch chamber of in the connecting ductto the gas manifold. When the rocket is ignited, the associated safetydoor or valve is caused to open, usually in response to the exhaust gas.The result will be the admission of exhaust gases into the manifold orexhaust duct and into the area surrounding the rocket itself. The doorsand valves associated with the system's launch tubes, containing rocketswhich are not being ignited, are normally maintained closed to preventcirculation of the exhaust gases. However, a malfunctioning door orvalve could allow exhaust gases from one tube to enter the other launchtube.

Such doors and valves have been disclosed, for example, in U.S. Pat. No.2,445,423 of Eastman which discloses a safety container for rockets. Thedisclosed hold-down doors consist of a one-way, two-flap check valvewith associated springs to hold the flaps closed. The blast of exhaustgases from the ignition of the rocket blows the check valve open andactuates the system.

A second rocket exhaust control apparatus has been disclosed inapplicant's prior U.S. Pat. No. 4,044,648. This patent discloses flowcontrol doors which are hinged and provided with counterweights so thatthey are normally closed, but open under gas pressure after rocketignition. The increased pressure in the exhaust duct will maintain thedoors of the other launch chambers in the closed position and protectun-ignited rockets which are being stored.

Another type of rear door for rocket launch tubes is disclosed inapplicant's prior U.S. Pat. No. 4,134,327. In this disclosure, the dooris latched open and normally remains open until the rocket is launched.A protective seal or cover will normally close the launch tube until themissile is fired. After firing the door is released by, for example, asensor as the missile leaves the launch tube. Gases from the launchedrocket can also be used to power the door closed and a latch is providedto hook the door in place and seal off the launch tube from theassociated plenum chamber after firing.

Still another apparatus for sealing launch tubes is disclosed inapplicant's prior U.S. Pat. No. 4,186,647. In this case, a covernormally blocking the connection between the launch tube and the duct orplenum is provided. The cover has at least one frangible center sectionwhich is broken in response to the pressure and temperature of theexhaust of the exiting rocket. The breaking of the section opens aconnection between the launch tube and the plenum. Thus, the systemseals the tube from the plenum prior to firing but allows the escape ofthe rocket exhaust gases after ignition.

Further reference is made to Betts et al U.S. Pat. Nos. 3,968,646,4,033,121 and 4,036,013. These patents disclose a rocket nozzle closurefor controlling release of pressure. The nozzle is arranged in a mannerwhich effects closing incrementally and continuously. As a resultthereof, release of pressure is controlled by the rate of change ofmomentum of the system.

SUMMARY OF THE INVENTION

In accordance with the present invention, an apparatus is disclosed forclosing an intermediate point in a launch tube for exhaust-propelledvehicles, such as rockets or missiles. The apparatus, in particular, isdesigned to seal against the end of the rocket for the time periodbetween ignition and lift-off, in response to the exhaust gas pressure.The seal is then broken and can be removed by impingement of exhaustgases on it as the rocket leaves the launch tube. In addition, theapparatus is designed to provide a secondary or back-up seal for launchtubes which have a primary seal more closely aligned with the junctureof the launch tube and plenum chamber or duct. This back-up systemprevents back flow of the exhaust gases of other rockets from reachingthe area around the rocket in question. The present invention, inaddition to providing optional rear doors such as those described above,provides a launch tube for a rocket that is closed by aflexible/ablative rear cover around the rear of the rocket inside thelaunch tube. Initially, the rocket exhaust flows through a circular areain a flexible cover and, due to the pressure increase produced by theexhaust gases, the cover is pressed against the rear of the rocket. Theresulting contact seals the upper area of the launch tube, that is thearea around the rocket itself, from the flow of the exhaust gases. Asupport screen is positioned above the flexible member and prevents theapparatus from distorting out of place and breaking the seal underordinary plenum gas pressures. Further, the seal distorts downwardlyafter lift-off and is optionally ablative as well as flexible duringlift-off of the rocket.

The downward flex, and thus the area available for exhaust gas flow,increases during launch as the rocket moves upward, causing thedistortion and/or the loss of material as the apparatus of the presentinvention tends to comply with the impact of the rocket's exhaust gases.The apparatus may be used alone, as it forms a seal between the plenumchamber and the majority of the volume of the launch tube in the system,or it may be used in conjunction with known sealing means whichordinarily seal the tube from the plenum chamber, such as thosedisclosed in applicant's previously discussed patents.

When an additional form of rear launch tube cover is used in conjunctionwith the seal of the present invention, the present seal provides aback-up system. In addition, during the time immediately after ignition,pressure is increased in the volume produced by the launch tube, thelaunch tube cover, and the seal of the present invention. Such pressurewill initiate the removal of material from the launch tube cover or openthe launch tube cover by other means. Further, without the seal of thepresent invention, it is possible for exhaust gases in the volume or inthe plenum to pass into the tube. The present seal is designed toprevent surge in the rocket direction and eliminate exhaust gas backflow into the tube during the launch period.

On the other hand, once the rocket has been launched and has left thetube, in the apparatus of the present invention, the connection betweenthe exhaust manifold and the launch tube remains open. Should thisproduce a problem, the type of door disclosed in applicant's prior U.S.Pat. No. 4,134,327, referred to above, could conveniently be used inaddition to the apparatus of the present invention.

The novel features that are considered characteristic of the inventionare set forth with particularity in the appended claims. The inventionitself, however, both as to its organization and method of operation, aswell as additional objects and advantages thereof, may be bestunderstood from the following description when read in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic side elevation view showing a plurality of launchtubes having rockets therein, one showing a stored rocket, oneillustrating a held-down rocket during ignition, and the other twoillustrating rockets in various stages of ascent;

FIG. 2 is an isometric view of the seal of the present invention; and

FIGS. 3A-3C are sectional schematic views of a portion of the seal inaccordance with the present invention showing, in FIG. 3A, the sealposition when stored, in FIG. 3B, the seal position immediately afterignition, and, in FIG. 3C, the seal position after lift-off.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and in particular to FIG. 1, a launchinstallation is schematically illustrated. The installation includes aplurality of launch tubes 10-13. It is understood that the number oflaunch tubes is arbitrary, and that more or fewer tubes may be provided,as desired. The launch tubes are capable of being connected to a commonduct or plenum chamber 15 for conducting exhaust gases, created by thelaunch of one of the rockets, away from launch tubes 10-13. It will, ofcourse, be understood that instead of rockets, missiles or otherexhaust-powered vehicles may be utilized.

Launch tube 10 illustrates rocket 16 disposed therein and held in placeby suitable hold-down devices (not shown). Such devices are well knownto those skilled in the art. The rocket is provided with exhaust gasnozzle 17 through which hot exhaust gases emerge after ignition. Thetube is also provided with supportive screen 18 which projects from thetube to the edge of rocket nozzle 17 and toward the rocket skin. Inaddition, flexible and ablative rear cover 19 is provided immediatelyadjacent to supportive screen 18 and also covers the area from therocket tube to the nozzle. It is also to be understood that flexiblecover 19 and supportive screen 18 need not necessarily abut the rocketnozzle or other portion of the rocket at all times. However, they mustbe in a position where, upon the application of pressure to cover 19from below, the cover supported by the screen will seal against theportion of rocket 16 that it is next adjacent. The bottom of launch tube10 is shown closed with one of optional cover members 20.

In tube 11, rocket 35 has just ignited and exhaust plume 38 is producingpressure on cover 19, closing the seal against nozzle 36 in accordancewith the present invention. Cover 19 is supported by screen 18 and heldin position to seal the remainder of the chamber. By reaching apredetermined pressure, or upon overcoming the pressure in plenum, 15optional cover member 24 completely opens and the exhaust gases pass outinto the plenum, as indicated by arrows 37.

After lift-off, rocket 40 in chamber 12 breaks the seal produced bycover 19 and screen 18 after nozzle 41 traverses the seal area. At thispoint, the seal of the present invention (cover 19) is deformedrelatively downward under the influence of the impinging rocket exhaustand initial removal of material from it may occur. In this portion ofthe illustration, the exhaust gases are continuing to flow in thepattern shown by arrows 37 and produce the above deformation andmaterial removal. Exhaust gases 37 from the plenum are pushing upward oncover 19 supported by screen 18 and are thus prevented fromrecirculating in launch tube 12 around rocket 40 due to the formation ofa seal.

In launch tube 13, rocket 40 has continued its upward motion and exhaustplume 44 has continued to deform and ablate cover 19 and possibly abradescreen 18. It is to be understood that screen 18 may also be ablativeand may be partially removed by the exhaust gases in the same manner ascover 19 which is more completely ablated. When the top of launch tube12 or 13 is open, by means not shown, air 61 outside of the launch tubeis aspirated into the top of the launch tube and conveyed to the viscousmixing region of the rocket exhaust. If the top of the launch tube isnot open, for example, during a restrained firing, pressure in launchtube 11 will decrease below its original value as the air in the launchtube flows into the viscous mixing region of the exhaust. Either ofthese above conditions is desirable and both are possible because of thefunction of cover 19 which prevents exhaust gases 37 from recirculatingback up into the launch tubes. It is understood that this is the casewhether additional cover member 24 is incorporated or not.

In FIG. 2, screen 18 and flexible ablative rear cover 19 are shown as asingle entity. It is understood that the apparatus is compatible withany launch tube cross-sectional geometry. The screen and cover areprovided with an annular orifice in the center which forms the seat forthe seal around the nozzle or the rear portion of the rocket.

In FIG. 3A, a slightly schematic section shows tube wall 48 havingattached thereto support screen 50. Support screen 50, in this detailedperferred embodiment, is provided with toroidal reinforcing lip 52around its aperture, the center of which is normally adjacent the end ofrocket 60. Flexible seal 54 is provided with annular sealing means 56,shown in the form of a cylindrical or conical lip in the area of theflexible seal next adjacent rocket 60. This seal portion is constructedin such a manner that when pressure is applied to the undersurface offlexible seal 54 it is deformed upward and sealing means 56 comes incontact with the base of the rocket. This contact produces the seal andprevents fluid flow upward into the area around the rocket itself. It isto be understood that the shape of the seal may vary depending on, forexample, the shape of the portion of the rocket with which the seal isto come in contact and the desired pressure build-up in the chamberproduced by the tube, the seal, and rocket and the cover of thisinvention.

FIG. 3B shows the position of the seal member immediately after ignitionof rocket 60. Pressure 61 has caused flexible seal member 54 to bedistorted upward and seal means 56 to come into contact with rocket 60,screen 50 and toroidal reinforcing lip 52, effectively preventing flowof exhaust gases in the upward direction. It is understood that this isthe condition during the entire rocket burn if, for any reason, therocket does not lift-off.

FIG. 3C shows the deformation of the system of the present inventionimmediately after lift-off, rocket 60 being displaced upward, relativeto the prior figures. Seal 54 and sealing means 56 are significantlydeformed in reaction to the impingement of exhaust gases 58 from above.This is the status of the sealing members of the present inventionimmediately after lift-off, and it is to be understood that once rocket60 has proceeded upward, exhaust plume 58 will be sufficiently wide toremove and/or distort part of seal 54 and sealing means 56, therebyincreasing the flow area through seal 54. If desired, part of screen 50and support torus 52 may be distortable or ablative. It is furtherunderstood that seal 54 and sealing means 56 continue to preventrecirculating plenum gases 61 from entering launch tube 48 in the areaadjacent rocket 50 as it proceeds upward. In addition, since the gasesare prevented from flowing into the adjacent area, the pressure producedby the recirculating plenum gases does not reach rocket 50. It isfurther understood that air 61 from the top of launch tube 48 willcontinue to flow through the launch tube and into the viscous mixingregion of exhaust 58 as the rocket proceeds upward.

Although there have been described above specific arrangements, offlexible area launch tube rear cover means between the tube of a rocketlauncher and the rocket itself, particularly usable in most systemsemploying multiple launch tubes and associated exhaust gas removalplenums, in accordance with the invention for the purpose ofillustrating the manner in which the invention may be used to advantage,it will be appreciated that the invention is not limited thereto.Accordingly, any and all modifications and variations which may occur tothose skilled in the art should be considered to be within the scope ofthe invention as defined in the appended claims.

What is claimed is:
 1. An apparatus for sealing a portion of a launchtube for exhaust-propelled vehicles and for allowing free flow ofexhaust gases after lift-off comprising:a launch tube; duct meansadjacent to said launch tube for conducting the exhaust of said vehicleaway from said vehicle; and flexible sealable means extending across atleast the open portion of the launch tube in the vicinity of the ductmeans.
 2. The apparatus of claim 1 wherein said sealable means comprisesa support member and a flexible seal member.
 3. The apparatus of claim 2wherein said members are located adjacent the exhaust of said vehicleand contain an opening of substantially the same size as an externalsurface of said vehicle.
 4. The apparatus of claim 3 wherein saidsupport member includes a toroidal lip at said opening.
 5. The apparatusof claim 3 wherein said support member is a screen and abuts the sealmember at said opening.
 6. The apparatus of claim 5 wherein said sealmember includes a conically shaped lip.
 7. The apparatus of claim 2wherein said sealable means is flexible and is distorted by the exhaustplume of said vehicle during launching.
 8. The apparatus of claim 7wherein said sealable means is ablative and is removable by the exhaustplume.
 9. An apparatus for sealing a portion of a launch tube forexhaust-propelled vehicles and for allowing free flow of exhaust gasesafter lift-off comprising:a launch tube; a duct disposed adjacent saidlaunch tube for conducting the exhaust of said vehicle away from saidvehicle; sealing means disposed from said tube to adjacent said vehicle;and a normally closed cover positioned substantially at the intersectionof said tube and said duct.
 10. The apparatus of claim 9 wherein saidsealing means and said cover initially form a closed chamber at theignition of the vehicle and said sealing means prevents flow of exhaustgases upward through said tube after ignition and lift-off.
 11. Theapparatus of claim 9 wherein said sealing means comprises a supportmember and a flexible seal member.
 12. The apparatus of claim 11 whereinsaid members are located next adjacent the exhaust of said vehicle andcontain an opening of substantially the same size as the externalsurface of said exhaust.
 13. The apparatus of claim 12 wherein saidsupport member includes a toroidal lip at said opening.
 14. Theapparatus of claim 12 wherein said seal member includes a seal at saidopening.
 15. The apparatus of claim 14 wherein said seal is conical inshape.
 16. The apparatus of claim 12 wherein said sealing means isflexible and is distorted by the exhaust plume of said vehicle duringlaunching.
 17. The apparatus of claim 16 wherein said sealing means isablative and is removable by the exhaust plume of said vehicle.